The present invention generally relates to measuring volume of fuel dispensed through a fuel dispenser. More particularly, the present invention relates to a fuel dispenser using a pressure sensor to measure a flow parameter and thereby determine if the amount of fuel being delivered to a vehicle corresponds to the amount being measured by the fuel dispenser.
In a typical fuel dispensing transaction, a customer arranges for payment, either by paying at the fuel dispenser with a credit card or debit card, or by paying a cashier. Next, a fuel nozzle is inserted into the fill neck of the vehicle, or other selected container, and fuel is dispensed. Displays on the fuel dispenser indicate how much fuel has been dispensed as well as a dollar value of the purchase. Dependent upon the timing and manner of payment for the fuel, either the customer terminates the flow of fuel into the vehicle by manually releasing the fuel nozzle, or the fuel dispenser automatically terminates the flow of fuel either at a pre-selected dollar amount or when the tank of the vehicle is full.
FIG. 1 is a schematic showing components of a typical prior art fuel dispenser 100. As shown, fuel is pumped from an underground storage tank 102 through a fuel pipe 104 to a flexible fuel hose 105 which terminates with a fuel nozzle 106 including a fuel valve 108. To initiate fuel flow, the customer manually activates a trigger on fuel nozzle 106 which opens fuel valve 108 so that fuel is dispensed into the vehicle. Fuel flow through fuel valve 108 is detected by a flow switch 116 which, as shown, is a one-way check valve that prevents rearward flow through fuel dispenser 100. Once fuel flow is detected, flow switch 116 sends a signal on communication line 124 to a control system 120. Control system 120 is typically a microprocessor, a microcontroller, or other electronics with associated memory and software programs. Upon receiving the flow initiation signal from flow switch 116, control system 120 starts counting pulses generated by a pulser 118. The pulses are generated by the rotation of a fuel meter 114 and are directly proportional to the fuel rate being measured.
As is known, fuel dispensers keep track of the amount of fuel dispensed so that it may be displayed to the customer along with a running total of how much the customer will have to pay to purchase the dispensed fuel. This is typically achieved with fuel meter 114 and pulser 118. When fuel passes through fuel meter 114, it rotates and pulser 118 generates a pulse signal, with a known number of pulses being generated per quantity of fuel dispensed. The number of pulse signals generated and sent to control system 120 on communication line 126 are processed to arrive at an amount of fuel dispensed and an associated cost to the customer. These numbers are displayed to the customer to aid in making fuel dispensing decisions. As well, control system 120 uses the information provided by fuel meter 114 to regulate the operation of valve 112 during fueling operations.
As shown, fuel dispenser 100 includes a turbine fuel meter 114, such as that disclosed in U.S. Pat. No. 7,028,561, which is hereby incorporated by reference in its entirety. With some turbine fuel meters 114, the possibility exists that the rotors (not shown) of fuel meter 114 can bind during use, yet still allow fuel to pass through the meter. As such, pulser 118 either does not create pulses or creates a reduced number of pulses than it should, meaning the flow of fuel can either go undetected or is detected at a reduced flow rate, respectively. Other designs of non-positive displacement type fuel meters can be prone to this same issue.
In addition to inaccuracies based on mechanical failures, it is not uncommon for thieves to attempt to steal fuel by disabling various components of typical fuel dispensers. For example, a thief may initiate fuel flow into a vehicle through fuel nozzle 106. After fuel flow is initiated, the thief disables pulser 118 such that either no pulses, or a reduced number of pulses for a given fuel flow rate, are reported to control system 120 along communication line 126. In this manner, the amount of fuel delivered to the vehicle either goes undetected or under-reported to control system 120, respectively.